I agree. But the habitability of our world has likely been evident to anyone with JWST-level technology for hundreds of millions of years, which might be enough to attract some interest in our solar system, maybe a beacon? The idea of tiny probes is interesting too. Something small could be sent near the speed of light, and could ‘grow’ like a seed in an energy-rich environment like our solar system. It’s nice to see this topic discussed without folks resorting to high-school humor (little green men, anal probes, etc.) for a change.
If we were visited hundreds of millions of years ago, the only way we could discover it would be if they left artifacts on the Moon. The Earth resurfaces itself too much for anything to survive.
I’ve had a story idea rattling round in my head for a while about the first people to explore a lunar lava tube, and when they go into one they discover an ancient telescope that was aimed through a skylight to observe the Earth, or that the lava tube was used to archive a whole bunch of stuff, isolated from cosmic rays and micrometeorites, perhaps for the use of humans once we developed the tech to find it.
I actually think that a lava tube on the Moon is probably the most likely place to find ancient alien artifacts, assuming any were ever left in our solar system. And inside a lava tube they could be perfectly preserved for millions of years.
Again: spacefaring civilizations don’t need to exist at the same time for it to be a Fermi paradox type problem. It’s not like a movie where if the bad guys die, everything they ever made has to dissolve or something. Their replicating probes, their megastructures, their beacons…no reason for them to not still exist.
Besides, once a species has gone interstellar, it’s difficult to see what could eradicate all of them. Singular threats like asteroids or gamma ray bursts won’t be sufficient. And societal / cultural issues also become far less of a threat as the colonies are so separate (of course, if FTL is possible then the colonies could still operate as one unit…but if FTL is possible, then the Fermi paradox gets a lot more serious).
Isn’t that more or less the plot of The Sentinel, the Arthur C Clarke story that 2001 is based on?
And not just JWST. There are proposals to send a telescope way out to the edge of the solar system and use the sun as a gravitational lense. In theory, it gives you megapixel resolution of planets up to dozens of light years away. You wouldn’t be able to read license plates, but you’d certainly make out land masses and major features.
Unless habitable worlds are extremely common in the galaxy, our planet would have been interesting to anyone with not much more than our level of development for the better part of a billion years.
I think that if habitable worlds that develop technology are extremely common, somebody would have already colonized our world, probably without our consent. Since that hasn’t happened yet, either we are one of the first to develop technology in our local space-time sector of the galaxy, or the development of technology is extremely rare. If the former, I feel bad about how humans might colonize our local sector. If the latter, I feel sad that we might be alone.
That is my usual position on this topic. I was just coming from the hypothetical position.
Why? The only thing that I feel bad about is that I will be unlikely be able to personally be able to see it.
Why sad about that? There’s plenty of diversity in humans to fill the universe.
Though here’s my thought. We go out to Europa, and we find life. And not just tiny microbes, but plants and animals; whales and fish and crustaceans abound.
Then we find that it evolved from tardigrades and spores from Earth.
Huh. Yeah, it sort of is, I guess. I haven’t read that in decades. Time to read it again!
Because colonization hasn’t gone well for the colonized in the only example we have, which is us.
Because we might not even know what diversity is yet.
Or we find that we evolved from tardigrades and spores. Do you think tardigrades evolved on Earth?
I’m not too worried about it. There is a difference between colonizing somewhere where people already live, and colonizing places where no one lives.
I mean, we do, so that’s an odd thing to say. And as we branch out, we will see even more.
We know that we didn’t evolve from them, and we do know that they evolved on Earth.
Sure. Leaving aside self-replicating probes, the rest of it falls under ‘artifact SETI’, where we go looking for remnants of dead civilizations rather than active signals. So far, we really haven’t had the capability to spot technosignatures of any civilizations below Kardashev level-3 that remake entire galaxies (which may not have ever existed). We *might be able to discover Dyson swarms now, but our ability to do so is very limited. We found Tabby’s star, which *could have been a Dyson swarm, so we know we could likely find them. We’ve only had that capability since Kepler, and have barely begun to look.
I still think there is room for debate about whether self-replicating probes are realistic. One thing that would make a huge difference is how dangerous the interstellar medium is. Estimates for rogue planets go as high as 100,000 per star in a galaxy. There may be as many as 100 million black holes in our galaxy. Given the cube root relationship between object size and frequency, that implies gargantuan numbers of smaller particles that could still destroy a space ship. Of course, the space between stars is also gargantuan.
If I draw a cylinder the width of my probe between here and a star light years away, what are the odds that a ship-killing obstacle is in that volume? Or that a mass large enough is close enough to deflect the probe off target? I’m planning to do the math, but it gets a big complicated and the numbers really aren’t known.
But exponential expansion is pretty improbabe if there’s a greater than, say a 90% chance that every probe sent out will not make it to its destination. Each probe would have to send out a fleet of probes to guarantee that at least one survives to its target.
What we know about the interstellar medium and interstellar travel is almost nothing. An answer to the Fermi Paradox can therefore always be, “there may be something preventing interstellar travel or exponential expansion that we have yet to learn.”
Play out the hypothetical - given enough time, and who knows how much is enough, intelligent civilizations with the technology to send out signals, or probes, and become spacefaring, will occur.
If no Great Filter or reason to hide then some civilization has to be first. That first out of the gate will only know they are that by the lack of finding any others. Well, if not first then they know no others are far enough ahead for signs of them to have yet been detected.
So we could be in that position. Run with it.
We expand. Knowing what we know about our species history do you see humanity having a Prime Directive to not interfere with evolving intelligent life or early civilizations? Or stomping any evolving civilization out before it becomes a threat? Would we bother sending a Klaatu and Gort to warn an emerging civilization to behave?
@Sam_Stone : I agree with all that. I agree that our ability to detect Dyson swarms and the like is limited, and recent.
And I agree that interstellar space might be incredibly treacherous…it’s an awful thought, essentially the Kessler syndrome, but played out across the entire universe, but could be true.
But, in terms of megastructures, beacons and the like, remember that Dyson swarms are just an example, not a claim of a specific thing that aliens will do. It’s an answer to the question: Can you think of any purpose for a megastructure?
The point with megastructures is that we don’t see anything beyond stars and stellar phenomenon that appear natural (even if we don’t yet fully understand them). We look out of the window and see fresh snow. Not only not things we’d recognize, like footprints, but no kinds of tracks whatsoever. Nothing *on* the snow either.
It’s not a proof against ETIs of course, but it is a reason to make us doubt that ETIs are common. And again, just so we’re clear: I would like nothing more than for ETIs to be common. I would love to live in a Star Control type universe (even though it means having some bad guys around…). But at the moment, it really doesn’t appear that we do.
If you look at the ocean, even for a long time, you might not see a single example of life. But it’s teeming with it.
It’s true that we haven’t seen anything unnatural in space, but first you have to ask yourself whatnwe could even potentially see,with the equipment we have - and it’s not much. There could be a civilization like ours a dozen light years away, and we would have no way of knowing. There could be Dyson swarms or other megastructures by the millions, and we just haven’t found them yet. There could all kinds of laser and radio signals, and we just haven’t looked or listened in the right places yet.
And if the galaxy is full of dead civilizations, we won’t know until we go there, if we ever do.
But in this analogy, we’re *in* the ocean, with a clear view across to the other side
Sure, but for all we know, the most useful megastructure a species could build is a Blibble Bridge, which would have been visible in the night sky even to prehistoric humans. We don’t know what the useful set of megastructures is.
The fact that we see no evidence of anything in the sky is an important data point, even if it’s true that our ability to probe, for example, gravity waves, is relatively new and rudimentary.
We can already see that no species in our, or nearby galaxies has built anything sufficiently “noisy” in the visible, radio, IR or MW part of the EM spectrum, or tried to modulate starlight in any kind of intelligent way.
Very speculative at this point, but are we really sure that megastructures like Dyson swarms or Dyson spheres aren’t out there? Maybe we shouldn’t be so sure …
It’s not about claiming to know there are no dyson spheres. It’s just about accepting that until now we had no evidence of ETIs and that set of lack of observation shouldn’t be handwaved.
In terms of this new paper, it’s very interesting, and I have my fingers crossed the same as anyone.
But every new astronomical phenomenon seems to go through a “This time is it aliens?” phase, I’ve seen it literally dozens of times, and I don’t even follow cosmology news that often.
No, I don’t think so. We’ve been brain washed by the SciFi genre into believing that there are a plethora of super civilizations out there that have evolved far beyond where we are. The fact is that many, many things have to go right for a civilization like ours to evolve and, once they do, they have to somehow survive the stage we have currently reached. That is the stage where our technical advances have far outstripped our emotional maturity.
Yes, I believe there is intelligent life and that races have achieved interstellar space travel, but “massive amounts” is a big overstatement to me.
Well, it depends on what “massive” means. There could be a number I’d consider stunning—say, in the millions—that’s actually pretty puny in universal terms.
Heck, you could have billions of advanced civilizations out there, and still have less than one per hundred galaxies. It’s a big, big, big universe.
Which is why I both consider the existence of nonhuman civilizations a near certainty, but am completely uncertain how close any might be.